One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,7)(4,6)(5,8)(9,10,14,18)(11,19,21,15)(12,16,22,20)(13,17,23,24)(25,26,30,31)(27,29,34,32)(28,36,38,33)(35,39,40,37)(1,2,4,6)(3,5,8,7)(9,11,14,21)(10,15,18,19)(12,17,22,24)(13,20,23,16)(26,31)(27,34)(33,36)(35,40)(1,2)(3,5)(4,6)(7,8)(25,26)(27,32)(28,33)(29,34)(30,31)(35,39)(36,38)(37,40) involution — undirected(1,3)(2,5)(4,8)(6,7)(9,11)(10,15)(12,17)(13,16)(14,21)(18,19)(20,23)(22,24)(25,27,30,34)(26,32,31,29)(28,35,38,40)(33,39,36,37)(9,12)(10,16)(11,17)(13,15)(14,22)(18,20)(19,23)(21,24)(25,28,30,38)(26,33,31,36)(27,35,34,40)(29,37,32,39)(9,13)(10,17)(11,20)(12,19)(14,23)(15,22)(16,21)(18,24)(25,29,30,32)(26,34,31,27)(28,37,38,39)(33,40,36,35)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.